Sod will_paginate library

I used will_paginate on an older platform :

activerecord (1.15.3)

activesupport (1.4.2)

acts_as_ferret (0.4.0)

ferret (0.11.4)

json (1.1.1)

radiant (0.6.2)

rails (1.2.3)

rake (0.7.3)

ruby-debug (0.9.3)

ruby-debug-base (0.9.3)

Fast Ruby debugger

Ubuntu Linux, Mysql.

I made a brand new installation with the following configuration :

actionmailer (2.1.0)

actionpack (2.1.0)

activerecord (2.1.0)

activeresource (2.1.0)

activesupport (2.1.0)

acts_as_ferret (0.4.3)

ferret (0.11.6)

json (1.1.2)

mysql (2.7)

rails (2.1.0)

rake (0.8.1)

No way : with gem install I got the following error : undefined alias_method?

Thus, I made a gem update rails, but the error persists.I then tried the plugin installation , and the error is now :

:

./script/../config/../vendor/rails/activesupport/lib/active_support/dependencies.rb:123:in `const_missing': uninitialized constant Deprecation (NameError)

from ./script/../config/../vendor/plugins/will_paginate/lib/will_paginate.rb:55

from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require'

from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `require'

from ./script/../config/../vendor/rails/activesupport/lib/active_support/dependencies.rb:147:in `require'

from script/../config/../vendor/plugins/will_paginate/init.rb:1:in `load_plugin'

from ./script/../config/../vendor/rails/railties/lib/initializer.rb:348:in `load_plugin'

from ./script/../config/../vendor/rails/activesupport/lib/active_support/core_ext/kernel/reporting.rb:11:in `silence_warnings'

from ./script/../config/../vendor/rails/railties/lib/initializer.rb:348:in `load_plugin'

... 13 levels...

from ./script/../config/../vendor/rails/activesupport/lib/active_support/dependencies.rb:147:in `require'

from ./script/../config/../vendor/rails/railties/lib/commands/server.rb:30

from script/server:3:in `require'

from script/server:3

Any clue ?

I really don't know what to do, except redevelop my own pagination plugin